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Diffusion-weighted magnetic resonance imaging for tumour response assessment: why, when and how?

Afaq A, Andreou A, Koh DM - Cancer Imaging (2010)

Bottom Line: The technique is quick to perform without the need for administration of exogenous contrast medium, and enables the apparent diffusion coefficient (ADC) of tissues to be quantified.Studies have shown that ADC increases in response to a variety of treatments including chemotherapy, radiotherapy, minimally invasive therapies and novel therapeutics.In this article, we review the rationale of applying DWI for tumour assessment, the evidence for ADC measurements in relation to specific treatments and some of the practical considerations for using ADC to evaluate treatment response.

View Article: PubMed Central - PubMed

Affiliation: Royal Marsden Hospital, Downs Road, Sutton, UK.

ABSTRACT
Diffusion-weighted magnetic resonance imaging (DWI) is increasingly being used to assess tumour response to a variety of anticancer treatments. The technique is quick to perform without the need for administration of exogenous contrast medium, and enables the apparent diffusion coefficient (ADC) of tissues to be quantified. Studies have shown that ADC increases in response to a variety of treatments including chemotherapy, radiotherapy, minimally invasive therapies and novel therapeutics. In this article, we review the rationale of applying DWI for tumour assessment, the evidence for ADC measurements in relation to specific treatments and some of the practical considerations for using ADC to evaluate treatment response.

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Related in: MedlinePlus

ROI placement. An ROI is typically drawn just inside the outer border of a tumour on the high b value MR image and then copied onto the ADC map. This is because tumour borders are usually better delineated on the b value images compared with the ADC map.
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Figure 6: ROI placement. An ROI is typically drawn just inside the outer border of a tumour on the high b value MR image and then copied onto the ADC map. This is because tumour borders are usually better delineated on the b value images compared with the ADC map.

Mentions: Solid, non-necrotic tumour tissues usually return low ADC values and effective treatment, as previously discussed, results in an increase in tumour ADC. To record tumour ADC values, a region of interest (ROI) is usually drawn to encompass the tumour of interest and the mean or median ADC value within the ROI recorded. ROIs can be manually drawn or by applying statistical region growing techniques available on some software. A few tips may be helpful with regards to ROI placement. First, as the tumour outline is usually better delineated on the high b value diffusion-weighted image compared with the ADC map, it is easier to mark out the tumour contour when the ROI is drawn on the b value image (Fig. 6). This ROI can then be copied and pasted onto the ADC map to record its value. Second, it may be desirable to draw the ROI just inside the outer border of the tumour to minimize any partial volume effects. Third, when comparing results before and after treatment, it is useful for the ROIs for both the pre-treatment and post-treatment scans to be drawn at the same sitting. This allows careful alignment of the images to match corresponding slice positions and ensure consistency in the approach to define the tumour contour. Fourth, although many studies have been performed using ADC results obtained at a single level through the tumour, it is worthwhile repeating ADC measurements at a few contiguous levels and then averaging the results to avoid sampling bias. Where available, the individual voxel values from each ROI can be pooled together, from which the mean or median ADC values of all the voxel evaluated can be derived. Last but not least, the choice of target lesion on which to perform ADC measurement should be made carefully and judiciously. The minimum lesion size amenable for ADC measurement should be at least twice the section thickness to avoid partial volume effects.Figure 6


Diffusion-weighted magnetic resonance imaging for tumour response assessment: why, when and how?

Afaq A, Andreou A, Koh DM - Cancer Imaging (2010)

ROI placement. An ROI is typically drawn just inside the outer border of a tumour on the high b value MR image and then copied onto the ADC map. This is because tumour borders are usually better delineated on the b value images compared with the ADC map.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2967137&req=5

Figure 6: ROI placement. An ROI is typically drawn just inside the outer border of a tumour on the high b value MR image and then copied onto the ADC map. This is because tumour borders are usually better delineated on the b value images compared with the ADC map.
Mentions: Solid, non-necrotic tumour tissues usually return low ADC values and effective treatment, as previously discussed, results in an increase in tumour ADC. To record tumour ADC values, a region of interest (ROI) is usually drawn to encompass the tumour of interest and the mean or median ADC value within the ROI recorded. ROIs can be manually drawn or by applying statistical region growing techniques available on some software. A few tips may be helpful with regards to ROI placement. First, as the tumour outline is usually better delineated on the high b value diffusion-weighted image compared with the ADC map, it is easier to mark out the tumour contour when the ROI is drawn on the b value image (Fig. 6). This ROI can then be copied and pasted onto the ADC map to record its value. Second, it may be desirable to draw the ROI just inside the outer border of the tumour to minimize any partial volume effects. Third, when comparing results before and after treatment, it is useful for the ROIs for both the pre-treatment and post-treatment scans to be drawn at the same sitting. This allows careful alignment of the images to match corresponding slice positions and ensure consistency in the approach to define the tumour contour. Fourth, although many studies have been performed using ADC results obtained at a single level through the tumour, it is worthwhile repeating ADC measurements at a few contiguous levels and then averaging the results to avoid sampling bias. Where available, the individual voxel values from each ROI can be pooled together, from which the mean or median ADC values of all the voxel evaluated can be derived. Last but not least, the choice of target lesion on which to perform ADC measurement should be made carefully and judiciously. The minimum lesion size amenable for ADC measurement should be at least twice the section thickness to avoid partial volume effects.Figure 6

Bottom Line: The technique is quick to perform without the need for administration of exogenous contrast medium, and enables the apparent diffusion coefficient (ADC) of tissues to be quantified.Studies have shown that ADC increases in response to a variety of treatments including chemotherapy, radiotherapy, minimally invasive therapies and novel therapeutics.In this article, we review the rationale of applying DWI for tumour assessment, the evidence for ADC measurements in relation to specific treatments and some of the practical considerations for using ADC to evaluate treatment response.

View Article: PubMed Central - PubMed

Affiliation: Royal Marsden Hospital, Downs Road, Sutton, UK.

ABSTRACT
Diffusion-weighted magnetic resonance imaging (DWI) is increasingly being used to assess tumour response to a variety of anticancer treatments. The technique is quick to perform without the need for administration of exogenous contrast medium, and enables the apparent diffusion coefficient (ADC) of tissues to be quantified. Studies have shown that ADC increases in response to a variety of treatments including chemotherapy, radiotherapy, minimally invasive therapies and novel therapeutics. In this article, we review the rationale of applying DWI for tumour assessment, the evidence for ADC measurements in relation to specific treatments and some of the practical considerations for using ADC to evaluate treatment response.

Show MeSH
Related in: MedlinePlus